theme 4a

Question 1

what is the blending theory of inheritance?

Answer 1

hereditary traits blend evenly in offspring through mixing of the parents’ blood

Question 2

what is transmission genetics?

Answer 2

the field of genetics that deals with the way genetic differences among individuals are passed from generation to generation

Question 3

what is the issue with the blending theory of inheritance?

Answer 3

if it were true, it would result in variation to be lost over time as extremes would only be produced when two organisms in the same extreme reproduce, which is unlikely

Question 4

what did Gregor Mendel do?

Answer 4

• tested hypothesis of blending vs. particulate inheritance

- used true-breeding varieties of peas

Question 5

what is a character?

Answer 5

a heritable characteristic, such as fur colour or seed shape. refers to the general category, not the type of characteristic itself (NOT brown fur colour)

Question 6

what is a trait?

Answer 6

a variation in character, such as brown fur colour or round seed shape

Question 7

what are P generations, F1 generations, and F2 generations?

Answer 7

P: parental.
F1: fillial, comes from P generation individuals reproducing with each other.
F2: offspring of the F1 generation

Question 8

what is dominance?

Answer 8

the masking of one allele by a different “stronger” allele

Question 9

what is the principle of segregation?

Answer 9

the idea that the pair of alleles that control a character separate as gametes are formed, so half the gametes contain one allele and the other half contain the other

Question 10

what is a homozygote?

Answer 10

an individual homozygous for an allele (has two identical alleles for one gene)

Question 11

what is a heterozygote?

Answer 11

an individual heterozygous for an allele (has two different alleles for one gene)

Question 12

what is a monohybrid?

Answer 12

a heterozygote for a single character

Question 13

what is a monohybrid cross?

Answer 13

a cross between two individuals that are both heterozygous for the pair of alleles

Question 14

what are Mendel’s 3 hypotheses?

Answer 14

the genes that govern genetic characters are present in two copies in individuals

if different alleles are present in an individual’s pair of genes, one allele is dominant over the other

two alleles of a gene segregate and enter gametes separately (diploid organisms get one allele from each parent)

Question 15

when is the probability product rules used?

Answer 15

for the probability of independent events occurring in succession (like the probability of rolling two 6s when rolling two dice at once)

Question 16

when is the probability sum rule used?

Answer 16

for the probability of any one of several mutually exclusive events occurring

Question 17

what is a testcross?

Answer 17

mating an individual with a dominant phenotype (but unknown genotype) to a recessive genotype to determine if it is homozygous dominant or heterozygous

Question 18

what do the results of a testcross indicate?

Answer 18

if half the offspring display the recessive phenotype, the tested individual must be a heterozygote

if all offspring displaythe dominant phenotype then the tested individual must be a homozygote

Question 19

what did Walter Sutton do? (general)

Answer 19

noticed parallels between Mendel’s principle of segregation and the behaviour of chromosomes during meiosis

Question 20

what parallels did Sutton notice between chromosomes and Mendel’s principle of segregation?

Answer 20

chromosomes occur in pairs in diploid organisms

chromosomes of each pair are separated and delivered singly to gametes

separation of any pair of chromosomes in meiosis and gamete formation is independent of the separation of other pairs

Question 21

what is the chromosomal theory of inheritance?

Answer 21

genes and their alleles are carried on chromosomes

Question 22

what is a locus?

Answer 22

the particular site on a chromosome where a specific gene is located

Question 23

what is incomplete dominance?

Answer 23

the phenotype of the heterozygous is an intermediate between the dominant and recessive homozygotes: the effects of recessive alleles can be detected to some extent in heterozygotes

Question 24

how are alleles labelled when they display incomplete dominance?

Answer 24

use uppercase letter for character and a superscript to identify the trait (instead of lower and upper case letters)

Question 25

what is the phenotype ratio produced by a monohybrid cross of a character displaying incomplete dominance?

Answer 25

1:2:1

dominant phenotype: intermediate phenotype: recessive phenotype

Question 26

what is codominance?

Answer 26

two alleles both have significant effects and both distinct effects are visible at once (not a mix of the effects, two distinct effects are seen)

Question 27

how are alleles labelled when they display codominance?

Answer 27

each allele gets its own letter and none of them are lowercase because none of them are recessive

Question 28

what are discrete traits?

Answer 28

traits that are either one or the other and can be clearly categorized with no overlap

Question 29

what are continuous traits?

Answer 29

traits that have a continuous distribution and cannot be neatly categorized. distribution forms a bell curve

Question 30

what causes traits to be continuous?

Answer 30

polygenic inheritance

Question 31

what is polygenic inheritance?

Answer 31

where several different genes contribute to a single character

Question 32

are phenotypes of polygenic traits dependent only on genotype?

Answer 32

no, also depends on environment

Question 33

what is pleiotrophy?

Answer 33

where a single gene affects more than one character